Electron discharge device of the velocity modulation type



June 27, 1950 L. J. DAVIES ETAL 2,512,887 ELECTRON DISCHARGE DEVICE OF THE VELOCITY MODULATION TYPE Filed Dec. 18, 1946 Inventors;

Leonard J. Davies,

Leonard Rushforth,

William D. Sinclair. Christopher J. Milner:

by R: a i

Their Attornex.

Patented June 27, 1950 ELECTRON DISCHARGE DEVICE OF THE VELOCITY MODULATION TYPE Leonard]; Davies, Leonard Rushforth, -Wil 1iam D. Sinclair, and Christopher JaMilner, Rugby, England, assignors to General Electric Com "many, a corporation of New York ApplicationDecem'ber 18, 1946, Serial No. 717,060

In Great :Britain 0otobe'r 29, 1941 "Section 1, Public Law'690, August 8,1946

Patent expires October '29, 1961 3-"Claims.

Our invention relates to electron discharge devices of the velocity modulation type inw-hich at least one resonating chamber is employedand in which high frequency electrical oscillations are developed by reaction with an electron beam. I

The resonating chambers employed in such devices may consist of hollow annular members having a circumferential gap along their portions of minimum diameter. The electron beam is projected across the gap and coaXially 'with the chamber. The-chamber may be of generally circular or rectangular shape 'in cross-section as desired. In some such devices two "or more resonating chambers arespaced alongin coaxial relation therewith.

Manufacturing difficulties *have hitherto been encountered in producing discharge-devices embodying such resonating chambers. The resonators frequently have beenconstructed .by machining two or more -parts from solid'metaLthe parts being assembled to 'form the resonating chamber. The envelope of the device is then completed by means of two sections of a glass envelope which are sealed coaxially on to the resonating chamber at-each end thereof, one of them carrying the electron gun and the other the electron'collecting electrode. It is important thatthe electron gun be so positioned "that the beam is accurately coaxial with the resonating chamber or chambers. provide an elongated hollow-collecting electrode which is coaxial with the chamber.

It is an object of the present invention to-provide a construction which facilitates the produc- 'tionand accurate assembly-of'such devices;

It isa further object/0f our invention'to provide an improved collecting electrode and mounting therefor. I

In accordance withthe illustrated-embodiment of the invention the resonating chamber is :made

by assembling two or mor'ep'arts within a'hollow casing to which at one endeither the electron "gun orcollecting electrode has been previously resonating-chamber or chambers, if two or more are used, which may previously'have been formed into an integral unit, if 'desired, may be accurately positioned "axially-within the outer casing 'by providing an internal shoulder on the casing against which the-unit is seated it being understoodthat' the external diameter o'f the resonat- It 'is also desirable to 2 ing chamber 'is "equal to, or slightly less than the internal diameter of the casing so thatthe two'are accurately fitted. At one end the casing is then provided with a neck portion tapering to a'fine edge -to which a cylindrical glass' member carrying a stem supporting the electron-gun -'issealed. At the other end of the casing a collecting electrode comprising an elongated tubular member is supported. "The electrode "is preferably-provided with anintern'al recess'ail'hic'ih has a depth equal to several timesits diameter to provide a field 'fr'ee region in whichthebeam 1s defocussed and which minimizes the liberationof secondary lectrons.

Our invention -will 'be better understood by reference to the following description taken in connection with the accompanying-drawing, and

its scope *will be pointed out in the appended claims. In the drawing, the single figure is an elevational view in section of an electric -=discharge device'embodying ourinvention.

Referring now to the drawing we have shown a velocity modulation electron discharge device *comprising an electron-emitting cathode I, a pair of resonating chambers f2 and 3, and an electron collecting electrode -*4. The resonating '9 into a narrow beam indicated *by interrupted "lines 0, whichis projected across thegap's, and

after passage through the gaps is, received by 'the collecting electrode d. The resonating chambers 2 and 3 are thus spaced axially along the beam.

"As isn'ow w'ell known-theelectronbeamduring ltspassage acrossth'e gap 1 (i-f its -mean velocity is suitably adjusted to the Width -'0f the :g-a- 'l,

causes oscillations to be produced in the reso- 'nating c'hamber 2, the frequency of which is pendent upon the-- rih-ys'ical dimensions of the chamber including i the -gap 1, causing high rrequ'ency potential variations to =oc'cur across the gap 1, which produce velocity modulation of the beam H]. The velocity mo'dul-ate'dbeam passing across the gap induces oscillations in the resonating cham'ber 3, the :ro'scillationsiiin the two chambers being caused to reinforce one another by means of the coupling loop II. The chambers 2 and 3 are further coupled 'bymeans of an array of apertures 6" in the transverse wall 6, the apertures being located on a circle the di- 4 ameter to provide a space of zero electrostatic field which thebeam enters and travels for a considerable distance thereby becoming defocussed ameter of which is approximately the mean dil tions :are of a very high frequency, it is impor' tant that the dimensions of the chambers should be accurately controlled within very fine limits since theresonating frequency of both chambers- The chambers are acshould be the same. cordingly constructed inseparable parts, each of which can be accurately machined, and these parts are inserted in an outer casing l2 forming part of the envelope of the'device. The casing l2 includes a main body portion, the inner diameter of which is equal to the outer diameter of the resonating chambers, provided with an internal shoulder l3, from which extends upwardly a cylindrical portion l4 terminating in a tapered rim 15 to which is sealed a stem E6 of glass or like insulating material on whichhas previously been mounted the electron gun including cathode I and electrodes 8 and 9. The gun ma thusbe accurately positioned coaxially with the portion M of the casing. The two resonating chambers are formed of an outer cylindrical shell 5 having the transverse wall ii above mentioned and two end walls I! and I8 respectively. The wall 6 ha a central aperture defined by tubular extensions 6' extending from opposed forces of the wall 6. Similarly the end walls l7, ill have tubular extensions I1, [8' defining central apertures therein. These three parts may b previously assembled with the members I1 and 18 received in recesses machined in the opposite ends of cylinder 5 so that their relativepositions can be accurately controlled, and therassembled parts are then inserted into the casing from the lower end thereof until the wall I! is against the internal shoulder I3. The parts are secured together by means of a ring l9 which may be threaded, if desired. e 1, ;The collecting electrode 4 is provided with a transverse flange 20 which is received in a recess at the lower end of the casing 12, thus completing the assembly of the device. If it is desired to operate the collecting electrode 4 at a direct currentpotential different from that of the resonant chambers, the flange 20 may be a body of glass. The previously assembled-output lead 2] is re.- ceived in a transverse aperture in the wall of the casing I2 and resonating chamber 3, and is secured in position, as by brazing.v The output leadis coupled into chamber 3 by a loop 2| and is sealed .in :a vacuum tight relation to the en velope by means of a body of glass 22.

As indicated, the resonating chambers may be provided with a jacket 24 and the collecting electrode with the jacket 25, through both of which jackets water may be circulated for cooling purposes. v

If desired, the parts may have the joints made vacuum tight in one operation after assembl by providing a brazing metal in contact with eachof the joints and baking the whole assembly at a temperature necessary to fuse the bnazing metal at all joints simultaneously. 1 7 The electron collecting electrode 4 is preferablyrecessedito .a depthseveral times the (11- Y due to the mutual repulsion'of the electrons. The electrons are thus collected more uniformly on I various parts of the internal surface of the collecting electrode and local heating is thereby avoided. There is also no field to assist in the liberation of secondary electrons and the emission of such electrons is minimized and most of those liberated :are collected on the walls of the collecting electrode.

While the invention has been described in connection with a device employing two resonating chambers, it is evident that one such chamber 7 only, or more than two maybe utilized. When only oneiresonating chamber. is used, the output lead will be coupled in to that chamber, while with three or more chambers, the output lead will preferably be coupled in to that nearest the collecting electrode, I l

In operation the resonating chambers and the collecting electrode, which are all electricall at a common potential, may be maintained at a high potential with reference to the cathode and thus form the firral anode of the electron gun. Preferably thecathode is maintained at a negative potential, the casing'b'eing at ground potential..

While we have described and illustrated :a particular-embodiment of our invention, it will be obvious to those skilled in the art that changes andmodifications may be inade without departing from our invention in its broader aspects and we therefore aim in theappended claims to cover rallsuch changes and modifications 'as fall within the true spirit and scope of our invention.

What we claim as new and desire to secure by Letters Patent of the United States is: 1. An. electric discharge device of the velocity modulation type including a cavity resonator provided by a plurality of cooperating parts, a hollow metal casing forming a part of an hermetically sealed envelope of the device and having an inwardly directed shoulder atone end, said cooperating parts being receivedwithin said casing and axially positioned by saidshoulder, a hollow elongatedelectron gun and'a collecting electrode sealed respectively to the opposite ends of said casing to complete the envelope of the device.

2. An electric discharge of the velocity modulation type comprising a hollow cylindrical casing forming a part of an hermetically sealed envelope of the device,- an electron gun sealed to one end of said. casing and a hollow elongated electron collectingelectrode sealed to the other end of said casing, a hollow cylindrical shell having its eX- ternal diameter substantially equal to the internal diameter of said casing," said shell being positioned within said casing and having a transverse wallzwith a central aperture therethrough defined bytubular extensionsextending from opposite faces of said wall-and end walls for said shell each having, a tubular extension defining a central aperture, said shell and end walls forming a pair of axially spaced cavity resonators, .the space between the adjacent edges of the tubular extensions from the transverse and end walls providing gaps across which a beam of electrons from the electron gun is projected.

3. Anelectric discharge of. the velocity modulation type comprising a hollow cylindrical casing forming a part of an hermetically sealed envelope of the device, an electron gun sealed to one end ofsaid casin and aih lowlelo g ted.electron collecting electrode sealed to the other end of said casing, a hollow cylindrical shell having its external diameter substantially equal to the inner diameter of said casing, said shell being positioned within said casing and having a transverse wall with a central aperture therethrough, an end wall for said shell and having a central aperture therethrough, one of said walls having a tubular extension surrounding the central aperture and extending into the resonator to define with the other apertured wall a gap across which a beam of electrons passes from said gun to said collecting electrode.

LEONARD J. DAVIES.

LEONARD RUSHFOR'II-I.

WILLIAM D. SINCLAIR.

CHRISTOPHER J. MILNER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PA'IENTS Certificate of Correction Patent No. 2,512,887 June 27, 1950 LEONARD J. DAVIES ET AL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 4, lines 47 and 48, strike out the Words a hollow elongated electron gun and a and insert instead an electron gun and an elongated;

and that the said Letters Patent should be read as corrected above, so that the same may conform to the record of the case in the Patent Office. Signed and sealed this 10th day of October, A. D. 1950.

THOMAS F. MURPHY,

Assistant Gammz'ssz'oner of Patents. 

